WE are on the banks of the Clyde at Pacific Quay on a perfect sunny day, the river calm and glittering.

The peace is spoiled only by the shrill sound of drilling coming from the ship in front of me. And what a ship she is. The Waverley may not be looking her best today - she is undergoing a pre-season MOT and spruce-up - but by the time she sails out into the Clyde later this month for the summer, this proud old lady of the sea will be gleaming.

On and below deck an army of sailors, engineers, apprentices and volunteers is undertaking the backbreaking work required to get everything shipshape for the start of this year's ruby anniversary season, which starts on May 21.

To celebrate, two anniversary sailings to Greenock that day will allow passengers to see the magnificent QM2 and, during the evening trip, the spectacular fireworks display that will mark the latter ship's visit to Inverclyde and operator Cunard's 175th anniversary.

On May 24, meanwhile - 40 years to the day of the Waverley's first public sailing in preservation - the boat will run the same timetable as it did in on that day in 1975, taking passengers from Glasgow to Largs, Rothesay, Tighnabruaich, Tarbert and Loch Fyne.

Since May 1975 the 68-year-old boat has taken more than five million visitors to sea, usually up and down the west coast of Scotland, although it's not just Scotland that gets to enjoy the Waverley - she also sails along the south coast of England and is particularly popular with Londoners as she paddles up and down the mighty Thames.

But the Waverley will always be known as Glasgow's boat, a vessel that plays a special part in the collective memory of the city and its people.

Nostalgia is a big part of the appeal. Many who grew up in the west of Scotland can recall days out with mums and dads, grannies and grandpas, sailing to places like Cumbrae, Bute and Arran, where pokey hats and fish teas would be enjoyed by all. Simple pleasures in a seemingly less complicated age.

But as anyone below deck will tell you, keeping Waverley afloat - both physically and financially - has never been easy, and she has been close to the disaster on both counts more than once in the past 40 years.

The woman charged with keeping everything ship-shape is Kathleen O'Neill, chief executive of Waverley Excursions, which operates the boat as part of a charitable trust. The 45-year-old former accountant, who lives in Glasgow's south side, has worked for the business for 20 years and been in charge for four, though she says that she is possibly less nostalgic than others since she had never stepped foot on the boat before taking the job.

Her right-hand man is the ship's captain, Senior Master Andy O'Brian, now in his ninth season in command.

O'Neill admits running a vintage boat such as the Waverley is tough, particularly when fuel is expensive and keeping up with the regulatory regime is challenging. She makes the point that she and the crew routinely work 14-hour days over the summer, and could earn significantly more in other industries or even on other boats.

"We are lucky in that ports in Glasgow, Argyll and Bute and Inverclyde give us free berthing," she says, "but it costs £12,000 a day on the Clyde to run the Waverley, which rises to £14,000 on the Thames. That's a huge amount of passengers to get up the gangway. The pressure is on and we can't always make the money to cover the costs.

"The rise in fuel costs has had a huge impact. At its peak, fuel cost 650 per cent more than when I started. Insurance costs have risen by £350,000 in that time, and winter refit costs by 450 per cent. That's got a lot to do with legislation, though obviously we are absolutely committed to safety."

Then there's that other torturer of seafarers - the Scottish weather. "Fuel is our single biggest cost," says O'Neill, "but the principal factor that dictates the success of the season is the weather."

O'Brian agrees with a seen-it-all smile and roll of the eyes. The 49-year-old, from Gourock, started his career at 16 as a gangway boy, and worked with CalMac before taking the wheel of the Waverley nine years ago. He leads a crew of 25 and admits being master of the ship is a challenge.

"Sailing the Clyde is very difficult," he says. "The weather affects us far more than it does the ferries - the seamanship required is considerable. But the satisfaction comes in rising up through the ranks, getting command of a ship and doing the job well. Of course, you also get to sail in some wonderful places.

"I remember calling Kathleen one day from Oban. We had 400 passengers on board, the sun was shining and the water was like a duck pond. That's what it's all about."

O'Brian's twin sons, Andrew and Iain, 24, work beside their father, making them the third generation of the family to work on paddle steamers.

The Waverley has charitable status, and receives donations from all over Scotland, the UK and abroad, but no substantial taxpayer subsidy, unlike some of the visitor attractions it must compete against. A number of councils give a small amount of funding as well as free berthing, and the vessel has received money from the Heritage Lottery Fund, including more than £3 million towards the rebuild of the ship between 2000 and 2003.

This year, more than £50,000 has been given by enthusiasts, while the work of apprentices donated by BAE and City Building has been vital in reducing the £110,000 needed to keep the ship seaworthy.

Today, spruce-up well under way, there are four City Building apprentices working on deck painting the outside of the cabins with a hard-wearing coating. Among them is 18-year-old Gemma Wright, from Riddrie in Glasgow, a second-year painting and decorating apprentice who has been on the ship for a month. She may be a teenager, but Gemma is aware of the position the Waverley holds in the hearts of Scots, especially Glaswegians.

"My granddad was really excited when I said I was going to be working on the restoration project," she smiles. "Apparently I was on the ship when I was a wee girl but I don't remember it. I'm definitely going to book a sail with my family. I enjoy coming here to work every day as it's completely different to painting a house or an office, and when the weather is nice it's amazing. It's great to work on something so iconic."

The contribution of the apprentices is crucial, as is that of the 100 or so volunteers. During the annual refit, a core team of 10 are regularly involved, among them a dentist - who is, unsurprisingly, particularly good at close drilling work - a retired nurse and a former Rolls-Royce engineer.

The latter, 83-year-old Gordon Johnstone, from King's Park in Glasgow, has been volunteering for seven years. Today he is helping maintain parts of the ship's 69-year-old engine. "I just love going doon the watter," he smiles. "To see the Waverley still sailing after all these years is great, and the beauty of the landscape never changes.

"I find the volunteering very therapeutic and it's a good chance to pass my expertise on to others. I'm booked on the ship for the first weekend of the season - I can't wait."

"The volunteers are vital," adds O'Neill. "They save us a huge amount of money, but they are much more valuable than that. They are our ambassadors - they love the ship and their contribution to its preservation is immense."

This year, as well as sailing the Clyde coast, the ship will go to the Hebrides, the Bristol Channel, the south coast of England and the Thames, before returning to home for the season's end.

Among the ship's biggest fans and most regular passengers are the actors Timothy West and his wife Prunella Scales, who have been active members of the Paddle Steamer Preservation Society for many years. West has described the Waverley as "a thing of beauty", and is active in vital publicity and fundraising.

So what does the modern Waverley passenger expect? Is it so different from the 1970s and 80s? The answer to this is yes and no, according to its chief executive. "Customers, even in one day, will look for different things," O'Neill explains. "Each day we sail for 12 hours and within that there will be trips aimed at different types of customer."

These different customers can include anything from school parties to groups of young people on a Saturday who want music and a drink on their passage to Rothesay, or families and the older crowd going to Dunoon or Largs and Ailsa Craig. On Sundays, the ship creates a relaxed atmosphere, with coffee, the papers, real ales and a roast on offer.

"We want to provide access for all to as many places as possible," says O'Neill. "We want people to use this amazing asset - after all, she's the last of her kind.

"People know what the Waverley is and have a great affection for her. For many, she reminds them of their childhood - there is a real nostalgia value. For others, though, it's just a good day out.

"We try to give people what they want. For some it is the serene scenery on a sunny day, the relaxation. Once you're on this ship, that's all you can do - there's no TV, no soft play, no Wi-fi. There aren't many places in this busy modern world where you can really get away from it all, but the Waverley is one of them.

"Her attraction lies in a mix of things - the heritage, history, social history, maritime history, engineering history, the scenery. But I think more than anything, it's just a great day out.

"This ship is about the people. She's beautiful, of course, but what's more important to me is what we bring to the people who sail on her, and what they give back. That's unique, and that's what keeps us going."

waverleyexcursions.co.uk